We focus upon behavioral mechanisms of drug action with the emphasis upon behavioral indicators of low-level drug and chemical toxicity. Our work is usually cast within a framework provided by longstanding interests in drug-behavior interactions and in behavior itself. Our experiments concern questions of both stimulus control and motor output. In the area of stimulus control, experiments are now underway with drugs such as the amphetamines to answers concerning the effects of such agents upon learned behavior under the control of discriminative stimuli of varying strength. The studies utilize both rats and pigeons. Although vision and hearing are the senses most often studied, the somatosensory system, partly because of apparent complexities and technical limitations, has received much less attention. We have developed facilities to study this system and now can explore drug effects on tactile sensitivity. Experiments with both large monkeys and humans are planned, with the human work being confined to the exploration of how digital block with a local anesthetic affects vibration sensitivity in the finger. Work also continues with psychotherapeutic drugs (e.g., haloperidol) that produce disorders of movement. These findings may provide clues to the etiology of drug-induced movement disorders.